Unit 3 Test

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1. If a mixture of NaOH has a pOH of 8.5. What is it's [OH] concentration?

2. Which of the following titrations might begin at pH = 11 and end with pH= 1?
a) strong acid with strong base
b) weak base with strong acid <-- Answer
c) weak acid with strong base
d) weak acid with weak bae
e) none of the above

3.The pH of a 1.25 x 10 ^(-3) mol/L NaOH solution is:
a) 7.00
b) 11.1 <-- answer
c) 12
d) 3.9
e) 4.9

4. In a titration between a strong base and a weak acid, would the buffered zone be from:
a) The starting point to when the solution reaches a pH of 7
b) The starting point to the ending point
c) The starting point to the equivalence point <---Answer
d) Both a) & c)
e) None of the above
(I thought that strong bases & strong acids didn't make buffering possible...If thats the case then how can there be a buffer zone in the first place? - Manuel)

I'm pretty sure (although I could be wrong so don't quote me!) that since you have the weak acid, you will get a buffer for that.Let's say it's CH3COOH + NaOH --> H20 + (CH3COO-)(Na+)
So the Na+ is from the buffer (it's called a "spectator ion" because it doesn't do anything, this is probably what you were thinking with the strong acid/base)
However, you still have the conjugate base (acetate ion), which will buffer the stuff. Hope this helps/is right!
Also, look at q.16 on this page. It supports my thinking.

5. What is the pH of salts?
a) depends on the salt<---
b) basic
c)neutral
d) acidic
e) none of the above

6. If a strong base is titrated by a weak acid, what would the pH of the equivalence point most likely be? (jiahua)
a) 2
b) 5
c) 8 <--- Answer
d) 12

7. Which is a property of a reaction that has reached equilibrium?
a) The amount of products is greater than the amount of reactants.
b) The amount of products is equal to the amount of reactants.
c) The rate of the forward reaction is greater than the rate of the reverse reaction.
d) The rate of the forward reaction is equal to the rate of the reverse reaction. <--Correct Answer

8. Given the reaction at equilibrium: N2(g) + O2(g) <-> 2NO(g) as the concentration of N2(g) increases, the concentration of O2(g) will
a) Decrease <-- Correct Answer
b) Increase
c) Remains the same
d) Increase then decrease
e) Decrease and increase ||

9. When a system at equilibrium is disturbed by adding more reactants, the system:
a) will shift to the right <---answer
b) will shift to the left
c) will do nothing
d) none of the above

10. When you add a stress of increased volume to a system at =bm, the system will:
a) shift to the right
b) shift to the left
c) shift to the side with more moles<---answer
d) do nothing

11. Given the reaction at equilibrium: 2 SO2(g) + O2(g) <-> 2 SO3(g) + heat
Which change will shift the equilibrium to the right?
a) Adding a catalyst
b) Adding more O2(g) <--Correct Answer
c) Decreasing the pressure
d) Increasing the temperature

12. When you add a stress of increased pressure to a system at =bm, the system will:
a) shift to the right
b) shift to the left
c) shift to the side with fewer moles <---answer
d) shift to the side with more moles

13) When you add a catalyst to a system at =bm, the system will
a) get to =bm faster <--answer
b) get to =bm slower
c) never get to =bm
d) shift to the right

14. A characteristic of a system at =bm is
a) it is reversible
b) it is closed
c) concentrations are constant
d) all of the above <---answer

15. A buffer must contain a mixture of:
a) a strong acid and strong base
b) a weak acid and its conjugate salt
c) a weak acid and a weak base
d) a weak base and its conjugate salt
e) b and d <----answer

16. Why is the pH of NaCH3COO greater than 7?
a) because CH3COO^- is a basic salt <----answer
b) because Na+ is basic
c) because water reacts with Na to make a basic salt
d) the pH of NaCH3COO is 7, not greater than 7

17. Which of the following is not a type of =bm?
a) Dissolution
b) phase change
c) chemical reaction
d) all of the ones listed are types of =bm <----answer

18. What is the Keq for the following reaction?
H2 (g) + I2 (g) <---> 2HI (g) (hilite for answer)
Answer: Keq=[HI(g)]^2 / [H2(g)] [I2 (g)]

19. In CuOH(s) <----> Cu+ + OH^- where Ksp=1.0X 10^-10, what is the [OH-] in a 1.0 M solution?
Ans: 1.0 X 10^-5

20.Name 2 qualities of acids and bases.
Acids: corrosive, sour, conductor
Bases: bitter, slippery, conductor

21: On a microscopic level, do molecules of solids dissolve when added to a saturated sol'n?
Ans: Yes, because it is a dynamic =bm so solids dissolve and the solution solidifies at equal rates.

22: What will the shift be when we add LiSCN to the following system: Fe^3+ + SCN <---> FeSCN^2+?
a) Left
b) Right <--ans
c) up
d)down
e) no shift

23: Would the reaction favor the products or reactants when the =bm constant is:
a) large? b) small?
and why?
ANS: a) favors products b/c the concentration of products is greater than the concentration of reactants
b) favors reactants b/c the reactants' [] is greater than the [] of the products

24. What would the Henderson-Hasselbalch eq'n be?
HCO3- +H2O <---> H3O+ + CO3^2-
Answer: pH=pKa(HCO3-) - log HCO3- / CO3^2-

25: Draw the titration curve for the addition of a weak acid to a strong base.

26. If a catalyst is added to the =bm then what does the =bm do to overcome the potential stess:
a) endothermic
b) exothermic
c) shift to the left
d) shift to the right
e) no change answer is e) no change